Charles Ellicott Commentary Deuteronomy 29:19

"and it come to pass, when he heareth the words of this curse, that he bless himself in his heart, saying, I shall have peace, though I walk in the stubbornness of my heart, to destroy the moist with the dry." — Deuteronomy 29:19 (ASV)

The imagination. —Rather, “stubbornness” or “obstinacy.” The word is only found here and in Psalms 81:12, outside the writings of Jeremiah, who uses it eight times.

To add drunkenness to thirst —that is, the indulgence of desire in addition to the desire itself; or, to add sin to temptation.

The Septuagint has a strange paraphrase: “So that the sinner shall not involve the righteous with him in destruction.” The thought seems to be that perhaps one idolater would not make much difference to Israel; he would never involve the whole nation in destruction. The drunkard could not be the ruin of the thirsty, so to speak; therefore, he might do as he pleased and, in fact, escape punishment, being protected by the general prosperity of Israel.

The quotation from the Epistle to the Hebrews admirably meets this mistaken view: “Lest any root of bitterness springing up trouble you, and thereby many be defiled.” The Targums render it as “to add sins of infirmity to sins of presumption,” a rendering that partly explains the Septuagint’s version.